Method of forming sheet glass color tube face panel with pleated skirt

ABSTRACT

A color television picture tube panel is fabricated of relatively thin sheet glass formed to define a substantially rectangular faceplate area surrounded by an upstanding flange having a fluted configuration over portions of its periphery. The end surface of the flange defines a seal edge for forming a glass-to-glass seal with a funnel having a seal edge of sufficient area to bridge the maximum peak to trough dimensions of the fluted portions. Methods of manufacturing such a panel are also described.

United States Patent 1191 1111 3,825,413 Schwartz July 23, 1974 METHODOF FORMING SHEET GLASS 2,699,014 1/1955 Steenis 65/107 x COLOR TUBE FACEPANEL WITH 3,381,347 5/1968 Reinwall, Jr. 65/61 X PLEATED SKIRT James W.Schwartz, Glenview, Ill.

Zenith Radio Corporation, Chicago, Ill.

Filed! Feb. 16, 1973 Appl. No.2 226,880

Inventor:

Assignee:

US. Cl 65/61, 65/58, 65/67, 65/107 -Int. Cl C03b 23/02 Field of Search65/58, 61, 67, 105, 106, 65/107 References Cited UNITED STATES PATENTS4/1903 Slevert 65/58 Primary Examiner-Arthur D. Kellogg Attorney, Agent,or Firm-Nicholas A. Camasto [5 7 ABSTRACT A color television picturetube panel is fabricated of relatively thin sheet glass formed to definea substantially rectangular faceplate area surrounded by an upstandingflange having a fluted configuration over portions of its periphery. Theend surface of the flange defines a seal edge for forming aglass-to-glass seal with a funnel having a seal edge of sufficient areato bridge the maximum peak to trough dimensions of the fluted portions.Methods of manufacturing such a panel are also'described.

4 Claims, 3 Drawing Figures METHOD OF FORMING SHEET GLASS COLOR TUBEFACE PANEL WITH PLEATED SKIRT BACKGROUND OF THE INVENTION This inventionrelates in general to color television picture tubes and in particularto glass envelopes for color television picture tubes.

The necessity of forming a phosphor mosaic image screen on the innersurface of the picture tube faceplate, which is capable of producinglight of three primary colors responsive to selective excitation,dictates utilization of picture tube envelopes which areseparable. Thepicture tubeenvelope consists of a panel or front section and a funnelor back section. The panel typically has an upstanding flange or skirt,which is useful for strengthening the panel, holding fluids used inscreening and manufacturing, providing a seal edge, and for supporting ashadowing electrode in predetermined relationship to the image screen.In conventional tri-gun picture tubes available today, the shadow masksupport consists of a plurality of inwardly directed studs embedded inthe panel skirt. The shadowing electrode is removable from the mountingstuds since, during normal screening operations, it must be inserted andremoved a number of times. The need for a separable panel portion, therequirement of supporting a relatively heavy shadowing electrode and thenecessity of withstanding high processing temperatures has resultedinthe panel being made .of exceptionally thick glass. As a result,'theglass envelope represents the major cost in manufacturing a colortelevision picture tube. The heavy thick glass panel imposes otherrestrictions on manufacturing since the various heating cycles must beprogrammed (in both heating and cooling phases) to preclude excessivestress buildup. In practice, substantial time is required for thegradual heat up and cool down cycles. With a panel of thinner glass, thetime required for heating cycles may be reducedand manufacturingeconomies effected.

SUMMARY OF THE INVENTION In accordance with the invention, themassiveness of the glass panel may be greatly reduced withoutdegradation of its strengthcharacteristics. This is achieved by makingthe panel with an upstanding partially fluted flange surrounding thefaceplate area. The fluted portions are readily formed in the upstandingflange or skirt in a simplified panel manufacturing technique andprovide desirable strengthening of the panel member. The resultantpanel, while being lighter, retains the requisite resistance todeformation during high processing temperatures encountered in colortube manufacturmg.

The seal edge or mating surface of the panel is formed by grinding ortrimming, since it must be relatively flat for frit sealing with thefunnel member. The seal edge, however, includes wavelike portions in thepanel corners, which requires the seal edge of the funnel to besufficiently large to bridge the maximum peak to trough dimensions ofthe flutes.

The fact that a panel configuration including fluted corners may be usedin conjunction with an appropriate funnel allows the panel to befabricated from sheet glass an economical technique not possible withconventionally shaped panels. Consequently, the fluted constructionenables manufacturing economiesas well as structural economies. IAccordingly, a principal object of this invention is to provide a panelfor a colorcathode ray requiring substantially less material than priorart panels.

A further'object of this invention is .to provide an economical panelfor a color cathode raytubecharacterized by fluted portions in the panelskirt.

Another object of this invention is to provide a panel for a colorcathode ray tube which is manufactured from sheet glass material formedwith fluted strengthening portions in the skirt.

' Other objects and advantages of this invention will become apparentupon reading the following description in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a glass envelopeincluding a par- 0 tially cutaway panel section constructed inaccordance FIG. 3 represents a partial enlarged view of the nel of FIG.1 taken along the lines 3-3.

DESCRIPTION or THE PREFERRED EMBODIMENTS fun- ' 12 although suchportions need not be restricted to the Spaced behind panel 10 is afunnel portion 16, in-

cludinga large bell-shaped portion 17 and a cylindrical neck portion 18terminating in a slightly flared portion 19. During a stage ofmanufacture, an electron gun .assembly will be inserted into neck 18 andsealed therein. In the process, flange 19 will be cut off. Funnel 17also includes a seal edge 20'for mating engagement withcorrespondingseal edge 13 of .panel 10. Seal edge 20 is flared in thecorners as shown at 21 to accommodate the fluted portions of panel 10.Except that funnel 16 includes flared portions in the corners along theseal edge and that panel 10 is made of thinner glass and has flutedstrengthening portions, the tube envelope is similar to those presentlyin use.

FIG. 2 shows a fluted portion of panel 10 in detail. The seal edge inthe fluted portions generally define a sinewave having maximum amplitudeat the diagonals of the panel and diminishing with increasing distanceaway from the diagonals. It is, of course, obvious thatthe glass fritused irn the glass-to-glass sealing step of the final tube manufacturebe capable of maintaining the requisite vacuum in the picture tube.Consequently, an enlarged sealing area is provided on the funnel sealedge to embrace the maximum peak to trough dimension of the fluted edge.The critical dimension is that 3 practical size is one that extends overthe fullran'ge of excursion of the flutes.

FIG. 3 is anenlarged view of the seal edge of the funnel in one comerwith a dashed line representation of fluted portion 12 of the panelsuperimposed to pictorially show the above relationship of parts. Thefunnel to panel sealing operation may be readily performed by laying abead of frit material on the panel seal edge following the flutedconfiguration. Alternatively, the frit seal may be made by laying a widebead of frit along the funnel seal edge, the frit'dimension being largeenough to surround the fluted glass portion of the panel.

A color tube panel in accordance with the invention lends itself todifferent techniques of manufacture also. Practically; a sheet ofglassmaterial of required thickness may be sagged over a form whichdefines the interior surface of the desired picture tube panel. As theglass sagsover the rectangular form, fluted portions or folds willdevelop in the corners. After the requisite degree of cooling, the sealedge is formed, preferably by cutting off unwanted material with a highpressure flame-(The seal edge may also be formed by a grindingoperation.) Mounting studs 15 may be inserted either as shown in FIG. 2,by locally softening the glass in the upstanding flange and pushing thestuds into position, or by the well-known technique of frittingl Itshould be understood that the orientation and position of the mountingstuds are determined by too] mechanisms (not shown) which areindependent of minor irregularities in the upstanding flange.

The panel may also be readily vacuum formed or pressed into theappropriate configuration while in the moldable state. The end result ofeach of these techniques is an economically manufactured panel ofrequisite strength but much lighter construction.

The provision of the fluted portions at the comers of the panel isessential to attain sufficient strength, especially to prevent warpingof the glass during tube manufacture. In particular, after the mosaicphosphor screen has been deposited using a suitable apertured electrodefor photoexposure any distortion of the panel will upset the criticalrelationship between the aperture mask and the phosphor screen.

For sealing purposes, however, it may be desirable to somewhat compressthe fluted portions while still in the moldable state to reduce themaximum peak to trough What has been described is a novel constructionfor a color television picture tube envelope. It is recognized thatnumerous modifications and changes in the invention may be made withoutdeparting from the invention as set out in the claims.

I claim: I 1'. The method of manufacturing a color television picturetube panel having a seal edge adapted to mate with the seal edge of apicture tube funnel, said method comprising the steps of:

heating a substantially flat piece of glass to its softeningtemperature; shaping said glass to have an upstanding flange havingfluted portions at the corners surrounding a substantially rectangularfaceplate area, the maximum peak-to-trough excursions of the flutescon-' stituting said fluted portions being dimensioned to lie within theembrace of the seal edge of the funnel; and

machining said panel to produce a substantially planar seal edge on saidupstanding flange.

2. The method of manufacturing a color televison picture tubepanel asset forth in claim 1 further comprising the steps of:

providing a form having a configuration corresponding to that desiredfor said faceplate area; and sagging the glass over said form to producesaid upstanding flange with fluted comers.

3. The method of manufacturing a color television picture tube panel asset forth in claim 1 wherein said upstanding flange is formed by avacuum forming process.

4. The method of manufacturing a color television picture tube panel asset forth in claim 1 wherein said upstanding flange is formed bypressing said glass into the desired shape.

1. The method of manufacturing a color television picture tube panelhaving a seal edge adapted to mate with the seal edge of a picture tubefunnel, said method comprising the steps of: heating a substantiallyflat piece of glass to its softening temperature; shaping said glass tohave an upstanding flange having fluted portions at the cornerssurrounding a substantially rectangular faceplate area, the maximumpeak-to-trough excursions of the flutes constituting said flutedportions being dimensioned to lie within the embrace of the seal edge ofthe funnel; and machining said panel to produce a substantially planarseal edge on said upstanding flange.
 2. The method of manufacturing acolor televison picture tube panel as set forth in claim 1 furthercomprising the steps of: providing a form having a configurationcorresponding to that desired for said faceplate area; and sagging theglass over said form to produce said upstanding flange with flutedcorners.
 3. The method of manufacturing a color television picture tubepanel as set forth in claim 1 wherein said upstanding flange is formedby a vacuum forming process.
 4. The method of manufacturing a colortelevision picture tube panel as set forth in claim 1 wherein saidupstanding flange is formed by pressing said glass into the desiredshape.